1, 3‐Dioxolane [MAK Value Documentation, 2018]. Issue 4 (19th October 2018) - Hartwig, A.
Abstract: The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) and the Pregnancy Risk Group of 1, 3‐dioxolane [646‐06‐0 ]. 1, 3‐Dioxolane causes a reduction in white blood cell count and in relative spleen weight at 1000 ml/m 3 and above in female rats after 13 weeks whole body inhalation. The NOAEC is 298 ml/m 3 . As the percentage of white blood cell count reduction is the same after four and 13 weeks, no decrease of the NOAEC after chronic exposure is expected. The former MAK value of 100 ml/m 3 was derived from the NOAEC. The MAK value is now lowered to 50 ml/m 3 which takes into account the increased respiratory volume at the workplace because the blood:air partition coefficient of 1, 3‐dioxolane is > 5 (see List of MAK and BAT Values, Sections I b and I c). Since a systemic effect is critical, Peak Limitation Category II is retained. The default excursion factor of 2 is retained as well, as no half‐life in blood is known. In a prenatal toxicity study in rats with gavage application, 1, 3‐dioxolane results in reduced fetal body weights and gross external, soft tissue and skeletal malformations or variations at 1000 mg/kg body weight and day. The NOAEL for developmental toxicity is 500 mg/kg body weight and day. After toxicokinetic scaling this dose corresponds to a concentration of 875 mg/m 3 (285 ml/m 3 ) at the workplace. The difference to the MAK value of 50 ml/m 3 is not sufficient. Therefore, the assignment to Pregnancy Risk Group B, for substances, for which damage to the embryo or foetus must be expected even when the MAK value is observed, is confirmed.